CFP - Docs - mMapValues

mMapValues

(mapperFn: MapperFn) => (collection: EntryCollection) => collection

Change each value of a collection

Consider mapValues instead.
This is for the uncommon case where mutating collection is required.

Try It

const arr = [1, 2, 3]
const inc = n => n + 1
const incrementAll = mMapValues(inc)
const mutatedArr = incrementAll(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [2, 3, 4]
const arr = [1, 2, 3]
const inc = (n: number) => n + 1
const incrementAll = mMapValues(inc)
const mutatedArr = incrementAll(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [2, 3, 4]

Try It

const arr = [1, 2, 3]
const inc = n => n + 1
const incrementAll = mMapValues(inc)
const mutatedArr = incrementAll(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [2, 3, 4]
const arr = [1, 2, 3]
const inc = (n: number) => n + 1
const incrementAll = mMapValues(inc)
const mutatedArr = incrementAll(arr)
console.log(mutatedArr === arr) // is true
console.log(arr) // is [2, 3, 4]

Sometimes we want to change each value based on a function. Below, we have a 20% sale across all soccer products in our store. Let's map the old prices to the new ones.

Try It

const soccerProducts = {
  soccerBall: 12.98,
  shinGuards: 9.94,
  cleats: 49.99,
}

const getSalePrice = compose([multiplyBy(0.8), roundToNearest('0.01')])
const applySale = mMapValues(getSalePrice)
applySale(soccerProducts)
console.log(soccerProducts)
// is {
//   soccerBall: 10.38
//   shinGuards: 7.95
//   cleats: 39.99
// }
type Products = Record<string, number>
const soccerProducts: Products = {
  soccerBall: 12.98,
  shinGuards: 9.94,
  cleats: 49.99,
}

const getSalePrice = compose([multiplyBy(0.8), roundToNearest('0.01')])
const applySale = mMapValues(getSalePrice)<Products>
applySale(soccerProducts)
console.log(soccerProducts)
// is {
//   soccerBall: 10.38
//   shinGuards: 7.95
//   cleats: 39.99
// }

Try It

const soccerProducts = {
  soccerBall: 12.98,
  shinGuards: 9.94,
  cleats: 49.99,
}

const getSalePrice = compose([
  multiplyBy(0.8),
  roundToNearest('0.01'),
])
const applySale = mMapValues(getSalePrice)
applySale(soccerProducts)
console.log(soccerProducts)
// is {
//   soccerBall: 10.38
//   shinGuards: 7.95
//   cleats: 39.99
// }
type Products = Record<string, number>
const soccerProducts: Products = {
  soccerBall: 12.98,
  shinGuards: 9.94,
  cleats: 49.99,
}

const getSalePrice = compose([
  multiplyBy(0.8),
  roundToNearest('0.01'),
])
const applySale = mMapValues(
  getSalePrice
)<Products>
applySale(soccerProducts)
console.log(soccerProducts)
// is {
//   soccerBall: 10.38
//   shinGuards: 7.95
//   cleats: 39.99
// }